The present invention relates to systems and techniques for controlling the local humidity of a sample, in particular in the field of macromolecular crystallography for the purpose of manipulating macromolecular crystals and for transferring macromolecular crystals from their growth wells to an X-ray diffractometer.
It is common for small (i.e. <1 mm) samples to be manipulated under a stereomicroscope (dissection microscope) for a variety of purposes, such as sample conditioning and sample mounting. A specific example concerns the manipulation of macromolecular crystals, which are typically grown in well plates (24 to 384 wells per plate). Each well is prepared with a solution of the macromolecule of interest and is sealed. Upon equilibration, the well may produce a crystal of the macromolecule. For analysis, the wells are usually opened to allow for mounting of the crystal and transfer to an X-ray diffractometer, using a variety of methods. In some cases, crystals must also be pretreated with solutions prior to mounting for cryoprotection or to provide a ligand of interest. These manipulations require exposure of the crystalline sample to the ambient environment. Such exposure of previously isolated samples to the ambient environment is common in many fields. For samples sensitive to ambient conditions (e.g. humidity and temperature), the exposure during manipulation under the microscope can be damaging to the sample.
Environmental chambers designed to be placed on a microscope are commercially available (e.g. chambers for live-cell imaging in fluorescent confocal microscopes and chambers for atomic force microscopy). However, these chambers are designed to house a sample and then control the environment of the sample during imaging. They cannot be effectively implemented for the types of sample manipulations under a stereomicroscope described above. Other related commercial products allowing for sample manipulation in a controlled environment are gloveboxes. However, these are large, expensive, and awkward, and therefore impractical for the manipulations described above. There is thus a need for a simple, compact, and quickly responsive approach for controlling the environmental conditions of macromolecular crystals and other similarly sized and sensitive samples during their manipulation under stereomicroscopes, allowing for high throughput and maximum dexterity of the researcher.